keesje
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Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Jul 20, 2009 2:55 pm

.
Hi, earlier this yr Rheinbote did a thread here on Civil Aviation on the Boeing 737/757 RS study http://www.airliners.net/aviation-fo...eneral_aviation/read.main/4286853/

However the complete article / details were not available by that time. Now they are  yummy  :
http://www.zinio.com/reader.jsp?issue=356227572&o=int&prev=sub&p=44

Some bullets :
 arrow  Boeing sees a market requirement Intra/Trans Asia, North America and Europe
 arrow  Twin aisles
 arrow  Short / medium haul, 2500-3200 nmi, Boeing resists calls for more range
 arrow  Around 757-300 capacity, 250-300 seats.
 arrow  Concepts were discussed with European Airlines
 arrow  Boeing acknowledges the 787-3 is compromised being a derivative of the long range 787-8
 arrow  Potential return to "more hydraulics"..

Good engines would IMO be crucial. I wonder if the LeapX / GTF could handle the required 40-43 klbs. Last week I started a more technical discussion on new engines / open rotor progress on Tech/Ops. http://www.airliners.net/aviation-forums/tech_ops/read.main/258685/

I have the feeling Airbus and Boeing purposely keeping a low profile but are all but sitting on their hands on the 737/757/A320 successors.

The enormous 737 / A320 backlogs IMO ain't what they look like, both Airbus and Boeing are cutting back production. Who wants to get their 737 in 2014 for use until 2039? Is it a smart investment?

The article seems to confirm the A321 and 737-900ER are not the 90% replacement for 757-200/ 757-300 /767-200/ TU154/ A300/ A310 some claim it to be. Of course airlines use 739/A321s, 757 wear out and there simply exist no alternatives at this moment.



Last month Airbus also indicated it is looking at broader solutions then just A320 series replacement. Quote of interest on the GTF : "Airbus is considering this new technology as a fallback technology should open-rotor not work out.  scratchchin 
http://www.ainonline.com/news/single...ptions-for-next-narrowbody-models/
"Never mistake motion for action." Ernest Hemingway
 
thegeek
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Jul 21, 2009 2:08 am

That's interesting. I have been wondering if there would be a market for a shorter range wide body, given that once the A330 goes out of production, there won't be any wide bodies on the market optimised for range less than 744 range, assuming the 787 & A350 meet their range targets.

It hasn't been tried since the A300.
 
panais
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Jul 21, 2009 7:06 am

It seems that Boeing has gotten the entire airplane design wrong. There is definitely something wrong with the way they make decisions.

They seem fixated at replacing their existing lines, 767 with the 787, 757 with this Light Twin, the 747-400 with the 747-8. To add to that they are considering replacing the 777 with another model. If they do a 737 narrow-body replacement, then there will be 5 families that they need to design, test, certify, built, deliver and support.

Airbus is getting it right.
A380 for VLA
A350 for Wide-body
A320 for Narrow-body.

Anything else is just fillers like the A330 for the missions that it is very good on.

They might have some gaps at the 250 seat narrow-body/widebody medium range or a 450 seat wide-body long range but you cannot be everything to everybody.
 
rheinwaldner
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Jul 21, 2009 12:02 pm



Quoting Panais (Reply 2):
It seems that Boeing has gotten the entire airplane design wrong. There is definitely something wrong with the way they make decisions.

They seem fixated at replacing their existing lines, 767 with the 787, 757 with this Light Twin,

I don't agree. That proposal is extremely bold. It would be the first dedicated shortrange widebody clean sheet design since the A300. It would serve a market that never has been lucrative and today is dead (as claimed by many users of this forum). The 753 was still too much plane to offer the efficiency this Y1.5 (good name Keesje!) could offer.

If this proposal is pursued it would mean that Boeing's strategy for the shorthaul business would be:
- Bet on a larger plane that is able to reduce the efficiency to unseen low levels at the cost of flight frequency (airlines would have to reduce the number of planes and the frequency if the overall capacity on the network should remain about the same).

I have experienced a lot of headwind just by illustrating the intention Boeing has. The idea that frequency should be sacrificed to get better efficiency is quite unpopular. The idea that this method should be used for short range traffic is completely off-limits to some.

For me the closest plane to Y1.5 is the A300. Not a stretch or a derivative but from the first penstroke a short-(not-more-medium-than-the-A320)-range-widebody!

The best thing to illustrate this is Boeing refusal to build in TATL range! We can only imagine how eager they are not to sacrifice efficiency for range:
How much would the efficiency penalty be if a 3000nm plane would be beefed up to offer Transatlantic ranges? One would assume not much, but Boeing refuses even to spend that small amount of performance at the cost of stellar short range efficiency!
 
roseflyer
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Jul 21, 2009 6:38 pm

The article is a touch outdated, but floating out the idea of a light weight twin aisle is an interesting concept. I don't see it personally working personally. There aren't that many airlines operating larger planes on shorter routes. I can think of a few in Europe, Asia and Australia, but not that many.

Quoting Keesje (Thread starter):


The enormous 737 / A320 backlogs IMO ain't what they look like, both Airbus and Boeing are cutting back production.

737 production has not been cut back. 777 production went down, but 737 is stable and has been since the last rate increase a couple years ago. It's at the highest rate it ever has been at.
If you have never designed an airplane part before, let the real designers do the work!
 
MSNDC9
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Jul 21, 2009 9:42 pm

757 replacement in a 2+2+2 config would be quite nice. Quick to turn and fall right between a 757 and 767 in fusealage diameter and length. Perfect for short haul routes between hubs and large markets or between to coast to coast large markets.
 
roseflyer
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Wed Jul 22, 2009 12:26 am



Quoting MSNDC9 (Reply 5):
757 replacement in a 2+2+2 config would be quite nice. Quick to turn and fall right between a 757 and 767 in fusealage diameter and length. Perfect for short haul routes between hubs and large markets or between to coast to coast large markets.

I would prefer it being 3 x 3 with a 3 inch wider seat instead of the extra aisle. I don't know if airlines agree.
If you have never designed an airplane part before, let the real designers do the work!
 
thegeek
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Wed Jul 22, 2009 12:55 am



Quoting RoseFlyer (Reply 4):
The article is a touch outdated, but floating out the idea of a light weight twin aisle is an interesting concept. I don't see it personally working personally. There aren't that many airlines operating larger planes on shorter routes. I can think of a few in Europe, Asia and Australia, but not that many.

Couldn't part of the reason for that be that there is no plane optimized for such a role?

I do agree, though, that stopping just short of a TATL range is probably a mistake.
 
keesje
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Wed Jul 22, 2009 7:35 am



Quoting MSNDC9 (Reply 5):
757 replacement in a 2+2+2 config would be quite nice. Quick to turn and fall right between a 757 and 767 in fusealage diameter and length. Perfect for short haul routes between hubs and large markets or between to coast to coast large markets.

Years ago I played with the idea. A little wider then A320 to enable 2-2-2 (which a percentage cinema like folding seats) and 2-1-2 premium for short trips and various other configurations for medium trips.

"Never mistake motion for action." Ernest Hemingway
 
thegeek
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Thu Jul 23, 2009 5:59 am



Quoting Keesje (Reply 8):
Years ago I played with the idea. A little wider then A320 to enable 2-2-2 (which a percentage cinema like folding seats) and 2-1-2 premium for short trips and various other configurations for medium trips.

Why are you obsessed with 2-2-2 in economy? The only way it could ever happen is if it could be shown that it's worth paying a weight & fuel penalty for faster turn times. I would doubt this. Also, there's nothing green about it.

I'd think that the best "Light Twin" would be around 3500-4000nm range, 2-4-2 in economy and LD3 containers in the hold. I.e. an A300, but with updated technology. Perhaps I am wrong.
 
TSS
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Thu Jul 23, 2009 6:24 am



Quoting Thegeek (Reply 9):
Why are you obsessed with 2-2-2 in economy? The only way it could ever happen is if it could be shown that it's worth paying a weight & fuel penalty for faster turn times. I would doubt this. Also, there's nothing green about it.

But that's only an extra half metre or so of width over 737/757 and A32x, which isn't such a big deal.

Quoting Thegeek (Reply 9):
I'd think that the best "Light Twin" would be around 3500-4000nm range, 2-4-2 in economy and LD3 containers in the hold. I.e. an A300, but with updated technology. Perhaps I am wrong.

That would be about a metre and a half wider than 737/757 and A32x which in my book is a wide-body and hardly a "light twin". Also, in a single-class layout that would be only 37 rows for 296 seats which would give the aircraft's fuselage a profile similar to a blimp: Great for rotation on takeoff, but probably not all that aerodynamically efficient at cruise.
Able to kill active threads stone dead with a single post!
 
rheinwaldner
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Thu Jul 23, 2009 1:32 pm



Quoting TSS (Reply 10):
wide-body and hardly a "light twin".

That must not be a contradiction. The structural efficiency of a widebody 300 seater should be better than that of a similarily sized narrowbody.

What is the best plane ever in the seat/MEW metrics? I assume the A300 is the best or one of the best.

For a 250-300 seater I would prefer a widebody. The range should have no influence on that design decision.

Quoting Thegeek (Reply 9):
I'd think that the best "Light Twin" would be around 3500-4000nm range, 2-4-2 in economy and LD3 containers in the hold. I.e. an A300, but with updated technology. Perhaps I am wrong.

I see the value of such a plane. Back to the roots! The first in this category (A300) set the standart!

I would expect stellar CASM of such a plane on short-to-medium routes. Maybe even the best CASM of any plane flying on this planet!
 
roseflyer
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Thu Jul 23, 2009 2:36 pm



Quoting TSS (Reply 10):

But that's only an extra half metre or so of width over 737/757 and A32x, which isn't such a big deal.

You don't think that is a big deal? That's probably 5% weight increase on the airplane with an off the cuff guess. Larger fuselage means beefier structure, not just more skin. 5% increase in weight means more than 5% increase in fuel burn. Why on earth would an airline want a 5% increase in fuel burn with absolutely zero increase in revenue potential? Is cutting 5 minutes off turn times going to recover that cost? Is it going to be so much drastically more comfortable that economy passengers (ie most cost sensitive) will go to it?

I think 2x2x2 is a dumb idea in economy. I doubt we'll ever see another twin aisle with less than 8 abreast.
If you have never designed an airplane part before, let the real designers do the work!
 
MSNDC9
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Thu Jul 23, 2009 4:32 pm



Quoting Thegeek (Reply 9):
I'd think that the best "Light Twin" would be around 3500-4000nm range, 2-4-2 in economy and LD3 containers in the hold. I.e. an A300, but with updated technology. Perhaps I am wrong.

You just described the 787-3 which has sold like hot cakes...
 
racko
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Thu Jul 23, 2009 5:51 pm

The 787-3 was too big to be a real A300 replacement. Remember, it would have been a variant of a ~8000nm aircraft, the A300 was purpose-built.
 
roseflyer
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Thu Jul 23, 2009 6:30 pm



Quoting MSNDC9 (Reply 13):

Quoting Thegeek (Reply 9):
I'd think that the best "Light Twin" would be around 3500-4000nm range, 2-4-2 in economy and LD3 containers in the hold. I.e. an A300, but with updated technology. Perhaps I am wrong.

You just described the 787-3 which has sold like hot cakes...

I still don't understand two aisles if you are below 8 abreast.

The problem with the wider fuselage is not the drag. Yes it punches a bigger hole through the air, but for less time. The big problem is that with engines on the wings, the size of the tail will keep increasing as the fuselage gets shorter. An 8 abreast 120 passenger plane is possible, but the rudder and elevators would have to be humongous and very heavy. The 737NG has a pretty hurkin big rudder in order to deal with the short moment arm due to the short fuselage and the high powered engine out scenario.

I don't want to seem too argumentative as I have quite a bit of respect for Keesje challenging the norms with aircraft design. However, I am an aircraft designer for a living and constantly have to evaluate many conditions when working on designs and take into account every factor. With aircraft design, it is almost assumed that the way it has always been done is better than new ways. You have to prove that a new concept is better. While airplanes might seem high tech, you'd be impressed if you looked at a plane to see the number of carryover parts from old designs. There are thousands of parts flying around newly built 737s and 747s that were drawn by hand in the 1960s by engineers. The technology for many things just hasn't changed that much. What has happened though is that those venerable designs have been refined and perfected over the years so that they can surpass the capabilities of newer technologies.
If you have never designed an airplane part before, let the real designers do the work!
 
thegeek
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Thu Jul 23, 2009 9:58 pm



Quoting MSNDC9 (Reply 13):
You just described the 787-3 which has sold like hot cakes...

Yes, but that's not exactly optimised for the purpose. Isn't it too heavy? Also, it's 8.5 abreast in economy, which mightn't be quite right.

And didn't that only come into being because the Japanese wanted a plane that could fit existing gates? History has taken a dim view of such planes.

37 rows & 296 seats isn't that much shorter than a 767-300, which in QF config has 40 rows. It's not that short really.
 
keesje
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sat Jul 25, 2009 8:41 am

thnx for your comments. Reasons to make a "light twin" a little wider then a 3-3 could be
* structural efficiency (I think a little wider fuselage could be lighter when it becomes this long)
* twin aisles isn't an extra, its solving a problem. NWA colleagues told me 757 disembarkation is pushing limits. A person at row 13 taking extra time is holding up 100 fellow passengers
* Long haul / premium cabin flexibility. For longer flights narrow 3 3 flights proved their restrictions. Wider cabin enables roomy 3 3, premium 2 1 2, pods, 1 2 1, etc.
* Cargo/luggage capasity is restricted. A wider cabin would facilitate A320 type cargo containers and pallets and bigger luggage bins.

There is more to it then just 2 2 2 in economy..
"Never mistake motion for action." Ernest Hemingway
 
PPVRA
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sat Jul 25, 2009 1:21 pm

Aside from capacity differences with the 783, sounds like it would be designed as a high-cycle widebody. Not the same kind of beast as the 783. I don't know if Boeing made changes to the 783 to increase cycles, if that's even feasible, but surely it wouldn't be optimized for short/medium-haul.

I like the idea overall, and if there isn't much of a market today, I think there will be. Congestion and lack of space for airport expansion will keep pushing the average size of aircraft up, at least at major airports.

[Edited 2009-07-25 07:01:22]
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tdscanuck
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sat Jul 25, 2009 2:56 pm



Quoting Keesje (Reply 17):
* structural efficiency (I think a little wider fuselage could be lighter when it becomes this long)

I'm not sure that works. At these size scales, you're probably sizing fuselage skin thickness by damage requirements, not strength, so you wouldn't gain anything on the skin. Frames would geat heavier. That leaves your stringers shrinking to make up for all the weight gain of the bigger skin. But the skin goes up with the square of the diameter increase, so I'm pretty sure you'll gain more skin than you'll save in stringers.

Quoting Keesje (Reply 17):
* Cargo/luggage capasity is restricted. A wider cabin would facilitate A320 type cargo containers and pallets and bigger luggage bins.

Definitely true, but you could also double-bubble for the same effect.

Tom.
 
keesje
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Jul 27, 2009 9:50 am



Quoting Tdscanuck (Reply 19):
At these size scales, you're probably sizing fuselage skin thickness by damage requirements, not strength, so you wouldn't gain anything on the skin

I think critical skin thickness would more be a restriction building a light 8 abreast airframe. Building a long tube you need the skin and structure to carry the load / moments induced by its lenght. Skin would likely be thicker then thinner then required to width stand external point loads. Long airframes like the A340-600 and B757-300 fusealges are relatively heavy because of it. More cross section would probably make them lighter.

A powerpoint of Greenliner, a more conventional configuration I made two yrs ago on a bigger, wider narrow body.
http://i191.photobucket.com/albums/z160/keesje_pics/greenliner-1.jpg?t=1248687630

I think on North Atlantic routes (Western Europe - Eastern USA) 230-250 seats two class such an aircraft could beat any existing / planned aircraft. OEW, drag, fuel consumption, pollution, operating costs all considerably lower then twin aisles like the A330-200, 787-8 and 767-300ER. But still with acceptable cabin / comfort levels, contrary to the 757's. Read trip reports on those Atlantic 757 flights..
"Never mistake motion for action." Ernest Hemingway
 
MSNDC9
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Jul 28, 2009 8:00 pm



Quoting RoseFlyer (Reply 15):
I still don't understand two aisles if you are below 8 abreast.

Like the 767?

Its clear the next generation narrowbody, even if 3+3 is going to be wider. Bombardier has already established the standard of seat width with Embraer steeping in first with the E-Jets, Boeing with the 787 and Airbus with the A350. So you have one of several new dimensions at play here:

In 3+3 Configurations:

Embraer Type Seat (18.25"): Minimum cabin width 143-144" (18" Aisle)
Bombardier (18.5/19"): Minimum Cabin width 148" (20" Aisle)
Boeing 787 Standard (18.5" Seat): Minimum cabin width 148-149" (21.5" Aisle)
Airbus 350 Standard (19.5" Seat): Minimum cabin width 153" (20" Aisle)

So lets call it 148" interior width

A 2+2+2 with the 18.25" seat (a good balance): 164"/18" Aisle
A 2+2+2 with 18" Seat: 162"/18" Aisle

Being 2+2+2 you can probably still get by with the 17.25" seat because people will feel less cramped then they do with the dreaded middle. That would be a 158" width.

Its not like several feet are being added here, and obviosuly the exterior width will be much larger, but it's going to be closer to the 757/A320/737 than it would be to a 767 and a lot faster to turn around up above 150 seats.
 
zvezda
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Aug 30, 2009 1:35 pm



Quoting Keesje (Reply 17):
twin aisles isn't an extra, its solving a problem. NWA colleagues told me 757 disembarkation is pushing limits. A person at row 13 taking extra time is holding up 100 fellow passengers

2-2-2 is not the optimal solution to faster disembarkation. Airbus and Boeing have both done tests and found that 3-3 with a 30inch aisle disembarks faster than 2-2-2 with two 20inch aisles. The reason seems to be that at about 30 inches, the aisle doesn't get blocked because there is enough space to get around passengers fumbling with their possessions. 20inch aisles are subject to blockage regardless of how many of them there are.
 
TSS
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Aug 30, 2009 2:10 pm



Quoting Zvezda (Reply 22):
Airbus and Boeing have both done tests and found that 3-3 with a 30inch aisle disembarks faster than 2-2-2 with two 20inch aisles. The reason seems to be that at about 30 inches, the aisle doesn't get blocked because there is enough space to get around passengers fumbling with their possessions. 20inch aisles are subject to blockage regardless of how many of them there are.

Which only makes sense. Also, there is usually more than one passenger fumbling with their possessions, so two 20 inch aisles could easily be blocked as well. Furthermore, a single 30 inch aisle would allow pax to get around the carts and make their way to the lavs during meal/drink service.
Able to kill active threads stone dead with a single post!
 
XT6Wagon
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Aug 30, 2009 5:03 pm

2-2-2 with 17.2" seats and minimum width asiles would require minimal extra width over a A320. The flexiblity from having that bit of extra width would be huge for airlines. The requirements for using containers for belly cargo are already a limiting factor on width, which is why it costs little to go that extra little bit and get flexiblity for selecting the seating they desire for thier own missions.
 
keesje
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Aug 30, 2009 8:10 pm



Quoting Zvezda (Reply 22):
20inch aisles are subject to blockage regardless of how many of them there are.

In my example I made a percentage of the middle seats fodable to make moving between aisles during (de)boarding possible.

With 2-2-2 airlines could select 3-3 if preferable (e.g. long flights). But more importantly is a capasity increase. It allows 5 abreast without a middle seat for short/medium premium class (e.g. US domestic F) and 4 abreast competitive business class seats (big seat with direct aisle access) for longer routes (e.g. transatlantic).

Thats a significant capasity increase for the same lenght over slightly narrower 3-3 optimized cabins.
"Never mistake motion for action." Ernest Hemingway
 
Flighty
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Aug 30, 2009 9:14 pm

This sounds totally pointless. A 767-200 or 767-300 SR are not what any airline really needs right now. They are insane, IMHO. It is probably misinformation.
 
thegeek
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 3:26 am



Quoting MSNDC9 (Reply 21):
Like the 767?

I've never understood the 7 abreast in the 767, and after learning more about planes I understand it less. You add all the weight for an extra aisle, but only get one more pax per row. Not only that, but you can't fit standard size containers. It's no wonder that the A330 beats the 767.

At the time the 767 came out, the only 8 abreast competition was the A300, and the only bigger planes were the DC-10/L-1011/747. The 767 had a nice niche in being longer range than the A300 and smaller than the other wide bodies at the time while not requiring a flight engineer.

Quoting Flighty (Reply 26):
This sounds totally pointless. A 767-200 or 767-300 SR are not what any airline really needs right now.

QF domestic is one airline which needs this plane.
 
Flighty
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 4:35 am



Quoting Thegeek (Reply 27):
The 767 had a nice niche in being longer range than the A300 and smaller than the other wide bodies at the time while not requiring a flight engineer.

Absolutely, the 763ER is still a great plane today. New ones are still being built.

Quoting PPVRA (Reply 18):
Congestion and lack of space for airport expansion will keep pushing the average size of aircraft up, at least at major airports.

IMO, at six abreast you can feed a great many people into airports with 739ER, or its successor.

Quoting Thegeek (Reply 9):

I'd think that the best "Light Twin" would be around 3500-4000nm range, 2-4-2 in economy and LD3 containers in the hold. I.e. an A300, but with updated technology. Perhaps I am wrong.

A330 orders suggest you're not wrong at all. But, airlines clearly want more range than that. Limiting such range is mad. They would lose so many orders due to the range limitation that it would essentially doom the product. The A330 is a nice product that does its job well, in Asia, Europe and America. Boeing already built its answer, called the 787. As a result I find this concept leading nowhere personally.
 
rheinwaldner
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 7:23 am



Quoting Flighty (Reply 28):
A330 orders suggest you're not wrong at all. But, airlines clearly want more range than that. Limiting such range is mad. They would lose so many orders due to the range limitation that it would essentially doom the product. The A330 is a nice product that does its job well, in Asia, Europe and America. Boeing already built its answer, called the 787. As a result I find this concept leading nowhere personally.

Therefore the focus lays on CASM.

Did you know that the A300 once reduced CASM by 66% over other short range planes of its time? Surely large shortrange planes don´t adress anybodies needs (maybe not more than a rather small niche). But offering a plane that reduces the cost on shortrange trunk routes largely may still have a considerable market. Many thousands A320 and 737 will be/were built. Beside those maybe 1000 large short range planes could find a buyer.

Of course such a short range plane would be a formidable platform, to get a efficient medium range plane later. A la A332 that followed the A333.

First version would be A332 sized but for shortranges. Second version would maybe have A310/767 size with TATL range and still mind blowing low CASM.
 
panais
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 7:51 am



Quoting Rheinwaldner (Reply 29):
First version would be A332 sized but for shortranges. Second version would maybe have A310/767 size with TATL range and still mind blowing low CASM.

The best option will be to take the A330-300, remove frames to the length of the A300 and then design a new composite wing and new landing gear that will take the weight down to about 75 tonnes which is about 15-20% of the original A300 weight.
 
keesje
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 8:13 am

A300-600 : Operating empty 120,150kg (264,875lb)
A330-200 : Operating empty 90,115kg (198,665lb)

The A330 (& 787) are for long range & very expensive for short/medium.

The replacement market (767, A300/310/Tu154/B757) is more then 2000. Few good short / medium haul replacements exist. US transcontinental, intra Asia, TransAtlantic, medium leisure flights worldwide, high volume city pairs are the markets that require such an aircraft.

IMO Airbus has a relatively straight forward optional scenario. New stretched composite wing & fuel capasity / landing gear, new GTF/LEAPX engines, reenforced mid fuselage section, Airbus A325/A326.. probably very good economics for a moderate investment.

"Never mistake motion for action." Ernest Hemingway
 
thegeek
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 8:42 am



Quoting Keesje (Reply 31):
A300-600 : Operating empty 120,150kg (264,875lb)

According to wikipedia, it's 90,900kg. About the same as the A332.

Where this concept could come undone is finding suitable engines. Would a cropped fan GEnx or Trent 1000 be suitable? I'm not convinced that a LEAP56 or IAE could scale to the required thrust, but I could be wrong.

Quoting Rheinwaldner (Reply 29):
Did you know that the A300 once reduced CASM by 66% over other short range planes of its time?

This couldn't be repeated today. That would compared to an early DC-9, 737-200 or 727-100. All of which had inefficient low bypass engines and low capacity, and in the latter's case didn't even dispense with the flight engineer (yes, I know the A300B4 had one two, but that cost was spread over more passengers).

Today, you'd have to be satisfied with more like a 10% CASM advantage
 
rheinwaldner
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 10:02 am



Quoting Thegeek (Reply 32):
Where this concept could come undone is finding suitable engines. Would a cropped fan GEnx or Trent 1000 be suitable? I'm not convinced that a LEAP56 or IAE could scale to the required thrust, but I could be wrong.

This is an important point. More and more we must think in thrust classes. Beside the 777 there exists no aircraft which set efficiency standards and/or was succesfull on the market which required a unique new "thrust class" (or in other words required engines to be developed only for itself). I see the following main "thrust classes":
- Narrowbody engines (for the 737 and A320 families)
- Widebody engines (the same thrust class is used for large quads or medium twins, 747, DC-10, 767, MD-11, A330, 787, A350, A380)

In these two thrust classes there is competition and market pressure. There is the largest progess. All the engine OEMs focus their research efforts there. The number of produced units is by far the highest. Even the number of 777 engines is marginal compared to the number of 747, 767, A330, 787, A350, A380 Engines.

Only around those hotspots independent developments from several manufacturers are possible.

The A340NG is an example of an aircraft which required a thrust class only for itself. Is it a good sign, that this light twin more or less requires the thrust of two A340NG engines? It means that we speak of a niche "thrust class" and a specific engine that never marked the efficiency benchmark and is trailing behind the volume models.

Quoting Thegeek (Reply 32):
This couldn't be repeated today

I know and agree fully. Big question is how much would it be? The result dictates the market prospects.
 
panais
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 10:02 am



Quoting Keesje (Reply 31):
A300-600 : Operating empty 120,150kg (264,875lb)
A330-200 : Operating empty 90,115kg (198,665lb)

More like....
A300-600 : Operating empty 90,115kg (198,665lb)
A330-200 : Operating empty 120,150kg (264,875lb)
 
keesje
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 4:00 pm



Quoting Panais (Reply 34):
More like....
A300-600 : Operating empty 90,115kg (198,665lb)
A330-200 : Operating empty 120,150kg (264,875lb)

I switched.  embarrassed  Key message is shortening / stripping an efficient long haul machine doesn't make it an efficient short machine. Ask Boeing (787-3).
"Never mistake motion for action." Ernest Hemingway
 
GST
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 6:38 pm



Quoting Thegeek (Reply 9):
I'd think that the best "Light Twin" would be around 3500-4000nm range, 2-4-2 in economy and LD3 containers in the hold. I.e. an A300, but with updated technology. Perhaps I am wrong.



Quoting Keesje (Reply 35):
I switched. embarrassed Key message is shortening / stripping an efficient long haul machine doesn't make it an efficient short machine. Ask Boeing (787-3).

Last semester at uni we had a design project for a new mid-widebody airliner designed to take long haul routes, but with one or more intermediate stops for refueling, (design range 2500-4000nm) meaning the aircraft needs to carry less fuel on any segment, meaning less structure for extra weight not there. The idea was to combine this with new tech to get a fuel saving for a LHR-SIN sortie in that was pushing 30% over existing airliners for novel solutions, and 15% for conventional designs. Factor that to be around 20% off each ticket price as a guestimate. When you are going to the Far East, would you be prepared to save £150 plus on your return ticket in exchange for about an extra hour in transit? I would. Most buisinesses might think it worth it too, maybe not all mind. The aircraft would also be perfect for high frequency (more than 1 flight per hour) routes with small aircraft (eg 737s), if an operator wanted to reduce frequency in return for being able to offer cheaper tickets. JFK-LAX springs to mind.

If you want to carry large numbers of people shorter distances there really isnt a new build competitor out there now, all the aircraft that have the capacity are also unfortunately blessed with too much fuel capacity and structure to give you sensible fuel bills.
 
MSNDC9
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Aug 31, 2009 10:41 pm

Quoting Flighty (Reply 26):
This sounds totally pointless. A 767-200 or 767-300 SR are not what any airline really needs right now. They are insane, IMHO. It is probably misinformation.

They don't want a 767-200/300 they have a 767-300 in the 787-8 and they want a 757-200/300 replacement with a bit more range and similar field performance - and they are not insane. It just depends on what the optimum cross section requirement is for it and a proper engine to drive its design and bring it forward - if that hasn't already been determined.

Quoting XT6Wagon (Reply 24):
2-2-2 with 17.2" seats and minimum width asiles would require minimal extra width over a A320.

Any future narrowbody with 6 across in any configuration will likely be wider than the A320.

[Edited 2009-08-31 15:45:34]
 
keesje
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Dec 01, 2009 5:00 pm



Quoting MSNDC9 (Reply 37):
Any future narrowbody with 6 across in any configuration will likely be wider than the A320.

I once thought Bombardier / operators might at some point fit 6 abreast Thompson seats in the C-series for short haul. Improving seatcount, pitch & elbow comfort. Have heard nothing since about such a CSeries configuration though  Wink

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metroliner
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Dec 01, 2009 6:06 pm

First off, Keesje, I must say, you do have a great sense of invention when it comes to aircraft. I hope you're either working in the industry or qualifying towards it!  Smile

However, I still don't 'get' the 2-2-2 concept. Sure, it's better for passenger comfort and there is a mootable increase in turnaround speed. Forgetting those two factors and going straight for CSM, why not put in 3-4 or 4-4 in a similarly-sized fuselage?

Cheers,

Toni
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Starlionblue
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Tue Dec 01, 2009 11:29 pm



Quoting Metroliner (Reply 39):
hy not put in 3-4 or 4-4 in a similarly-sized fuselage?

You can't have more than 3 abreast without an aisle on both sides due to evacuation requirements.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
metroliner
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Wed Dec 02, 2009 12:23 pm



Quoting Starlionblue (Reply 40):
You can't have more than 3 abreast without an aisle on both sides due to evacuation requirements.

I must admit I didn't know that, Starlionblue, but surely the duty of progress is to facilitate change?  Wink
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DocLightning
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Wed Dec 02, 2009 8:02 pm



Quoting Metroliner (Reply 41):

I must admit I didn't know that, Starlionblue, but surely the duty of progress is to facilitate change? Wink

Not when that change puts people in danger. A evac will always be a evac, no matter how advanced aircraft get, and so people need to get out.
-Doc Lightning-

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metroliner
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Fri Dec 04, 2009 3:27 pm



Quoting DocLightning (Reply 42):
Not when that change puts people in danger. A evac will always be a evac, no matter how advanced aircraft get, and so people need to get out.

I acknowledge that. But there's no reason to believe that we will never have an evacuation procedure that doesn't allow us to safely evacuate a row of four from a window. That's just the present regulation.
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Starlionblue
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sat Dec 05, 2009 5:10 am



Quoting Metroliner (Reply 43):
Quoting DocLightning (Reply 42):
Not when that change puts people in danger. A evac will always be a evac, no matter how advanced aircraft get, and so people need to get out.

I acknowledge that. But there's no reason to believe that we will never have an evacuation procedure that doesn't allow us to safely evacuate a row of four from a window. That's just the present regulation.

Sure. But you'd have to prove that you can evacuate in 90 seconds and just as "easily" as today. Someday the paradigm might change, but currently the only solution I see is more pitch so people can just run out into the aisle. That ain't happenin...

Unless, of course, you put an emergency window exit on each row.  Wink
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
metroliner
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Dec 06, 2009 10:11 am



Quoting Starlionblue (Reply 44):
Unless, of course, you put an emergency window exit on each row.

Ah, like in the old slam-door trains we used to have in the UK (only finished in 2007 I believe, and some still running!).  Smile
Set the controls for the heart of the Sun
 
GST
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Dec 06, 2009 11:12 am



Quoting Starlionblue (Reply 44):
Unless, of course, you put an emergency window exit on each row. Wink

Good god the extra weight that would add would be terrifying. There is a LOT of extra structure around any door on a pressurized aircraft, much much more than the average window.
 
thegeek
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Dec 06, 2009 10:41 pm



Quoting Starlionblue (Reply 44):
Sure. But you'd have to prove that you can evacuate in 90 seconds and just as "easily" as today. Someday the paradigm might change, but currently the only solution I see is more pitch so people can just run out into the aisle. That ain't happenin...

I wonder what the regulators would think of the once proposed (on a.net) 50% wider aisle in a narrowbody? Might go some way to helping the evac problem.
 
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Starlionblue
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Sun Dec 06, 2009 11:27 pm



Quoting Thegeek (Reply 47):
I wonder what the regulators would think of the once proposed (on a.net) 50% wider aisle in a narrowbody? Might go some way to helping the evac problem.

It might indeed. However (and I speculate here) I don't think the aisle is the bottleneck in this case. It's the length and narrowness of the passage between seat rows.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
keesje
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RE: Boeing Clean Sheet Y1.5 "Light Twin" Study

Mon Mar 01, 2010 5:20 pm

The "Light Twin" surface again.

"Yet, one of the reasons why Pratt & Whitney has "gone as high as 40,000lb of thrust is" that there are "airlines out there looking for a light twin", P&W vice-president next generation product family Bob Saia told ATI and Flightglobal last week during an exclusive interview in Dallas, where the engine manufacturer held a customer forum to exhibit some of its GTF hardware.

These airlines are interested in an aircraft with an "[Airbus] A320, A321 seating capacity, so 170 to 220 seating capacity" that offers a twin-aisle configuration, says Saia adding: "The reason for the twin aisle was two-fold - cabin comfort, but another is can you turn the aircraft around faster in terms of boarding and de-boarding."

It remains to be seen if airframers will pursue development of a twin-aisle narrowbody. Despite pressure from airlines to define their narrowbody replacement plans, Airbus and Boeing have instead been developing their current programmes to improve efficiency. Both airframers are looking at the possibility of re-engining their highly-successful narrowbodies, with decisions expected this year.

http://www.flightglobal.com/articles...isle-narrowbody-pratt-whitney.html
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